Abstract The overall aim of this paper is to examine the impact of ideologies and norms on a legal system. Against a background of a description of the hierarchy of norms in Swedish labour law and in European Union law, respectively, the paper aims to specifically demonstrate the problems caused by the different hierarchies of norms when implementing EU directives in Swedish labor law. The research question examines how the trade unions? right to industrial action towards an undertaker providing transnational services by posting of workers, is affected by the implementation of the Directive 96/71/EC of the European Parliament and of the Council of 16 December 1996 concerning the posting of workers in the framework of the provision of services. The paper answers the question under what conditions the Swedish trade unions have the right to take industrial action in situations of posting of workers. Through the study of sources of law and adhering to traditional jurisprudence, this paper investigates the legislation regarding trade unions? rights to take industrial action in situations of posting of workers. In addition to the jurisprudential research, a glance at the history of ideologies is provided.